Prevalence of family histories of breast cancer in the general population and the incidence of related seeking of health care.

Breast cancer is the most widespread cancer in women in western countries, currently accounting for one third of all cancers in women. 2 The lifetime risk of developing breast cancer is 9% in the United Kingdom, 10% in The Netherlands, and 12% in the United States. About 15%–20% of all cases of breast cancer are thought to be familial, 6 and about 5%–10% of all breast cancers are attributed to the known breast cancer susceptibility genes BRCA1 and BRCA2. In most European countries nationwide breast cancer screening programmes are available for women of 50 years and older, whereas comprehensive screening for breast cancer in women under the age of 50 has been found cost ineffective. It is widely acknowledged that women who have relatives with breast cancer have an increased risk of developing breast cancer themselves. 12 Consequently, screening for breast cancer might be advisable and cost effective in the subgroup of women under the age of 50 with a familial predisposition to breast cancer. We therefore started a study on the cost effectiveness of breast cancer screening in women under 50 with a familial predisposition to this cancer. For this study we needed information on the distribution of family histories of breast cancer among women under the age of 50 in the general population who might visit a healthcare doctor with concerns about their family history of breast cancer. Several studies have reported information on the percentage of women with a family history of breast cancer among cases of breast cancer and healthy controls. However, no such information is available for the general population. Other researchers have made attempts to gain information on the percentage of women in the general population who might be at an increased risk for breast cancer by using a family history questionnaire. The response rate to the questionnaire was, however, too low to draw useful conclusions. We have chosen to simulate a general population to gain this information. The aim of this study was to estimate the prevalence of family histories of breast cancer among women aged 30–50 in the general population and to compute the incidence of related seeking of health care.